As a method for realizing reduced bit cost of a nonvolatile semiconductor memory device and also enhancing memory performance thereof, scaling down of a memory cell is effective. However, there are increasing technical difficulties in scaling down the memory cell.
It has thus been proposed to use organic molecules for a charge storing layer of the memory cell. Because it is possible to organically synthesizing a variety of molecular structures and substituent groups, organic molecules may acquire desired electrochemical properties. And, because constitutional unit of organic molecules is small, it is possible to realize scaling-down of the memory cell by applying organic molecules.
In a nonvolatile semiconductor memory device using organic molecules for its charge storing layer, further improvement in charge retention properties is desired.